Striking or hammering tool



Patented Apr. 8, 1930 UNITED srnrs 'H" FFICE ERNST HJ'ALMAR WALODDI WEIBULL, OF SALTSJQBADEN, SWEDEN, ASSIGNOR T0 AKTIEBOLAGET NORDISKA ARMATURFABRIKERNA, OF STOCKHOLM, SWEDEN, A.

LIMITED COMPANY STBIKING 0R HAMMERING TOOL Application filed. January 14, 1928, Serial No.

The present invention relates to an arrangement in striking or hammering tools of the kind, which contains a striking or hammering body rotated by any suitable source of power. Said striking body which is arranged to reciprocate and cooperates with an anvil, is imparted a recoil movement by the stroke against the anvil and is during this recoil movement forced to store energy or perform a certain work by compressing air at one side of the striking body or by rarefying the air at the other side or both respectively. In striking tools working in this manner, as experience has shown, a decreased compression caused by air leaking out at the pressure side or a decreased vacuum at the suction side will readily arise, by which fact the regular work of the striking body will be made impossible.

According to the present invention this inconvenience is removed by the fact that the chamber in which the air is compressed or rarefied respectively, when the striking body, at the stroke against the anvil, is thrown back in the direction towards its rear position, is caused to communicate with the open air when the striking body again approaches its anterior position (striking position) so as to allow the atmospheric pressure in the chamber in question to be restored.

The annexed drawing shows in Figs. 1 and 2 two embodiments of a striking tool carried out according to the invention. Figs. 3 and 4c are side elevations of the striking body and anvil, respectively, removed from the tool frame and turned through an angle of 90 with respect to the position in which they are shown in Figs. 1 and 2.

The arrangement shown in Fig. 1 is based upon energy storing by means of rarefying the air in a chamber located in front of the striking body.

1 is the tool frame which has its rear end provided with a handle 2. 3 is the stator winding of an electric motor, the rotor 1 of which is arranged on or integral with a casing or a guiding part 5 arranged to support the striking body 6 to rotate therewith and to move axially thereof. The striking body is caused to partake in this motion of rotation by means of ribs 7 which engage with grooves 246,901, and. in Sweden September 21, 1927.

The gulding part 5 overlies the top end of the anvil 9, so as to form a chamber 12 in a more or less air-tight way although its size is varied according to the position of the striking body 6. At the recoil movementof the striking body the air will, on account of such movement, be rarefied in the chamber 12.

If no particular steps were taken, the pressurein the chamber would, however, gradually be changed by air leaking in, so as to produce a certain overpressure in the'chamher when the striking body 6 occupies its anterior position, which circumstance would, by its turn, bring along a reduction of the striking power of the striking body.

] In order to-remove this inconvenience a chamber 13, located behind the striking body 6, communicates according to the invention with the open air by means of apertures 14, and at the same time the guiding part 5 and the striking body 6 are shaped in such a manner as to allow the chamber 13 behind the striking body, to communicate, when said body occupies its anterior working position, by means of the grooves 8,with'the anterior chamber 12 through portions 15 of the groove 8, laid bare by the striking body. 'By the overpressure taking place in the chamber 12 at the end of the striking movementof' the striking body, an equalizing to atmospheric pressure will, thus, by this fact automatically take place so as to allow a continuous work to be maintained.

In the embodiment shown in Fig 2 the arrangement is such that the energy storing by the striking body is effected by compressing the air behind the striking body.

c As in the previous case, 5 is the guiding These 7 part, 6 the striking body provided with ribs 7 which run in grooves 8. 9 is the part or anvil receiving the stroke, said part or anvil being mounted to slide in the frame 1. 10 and 11 are the oblique faces. 16 is a quite closed chamber located behind the striking body. In this chamber the air is compressed. In order to prevent the air from being partly expelled out of this chamber so that the compression is gradually reduced at the recoil movement of the striking body 6, the striking body 6 and the grooves 8 are, also in this case, adjusted in such a way in relation to each other as to allow the chamber 16 to communicate with the open air (through the apertures 17) by means of portions of the grooves 8, laid bare by the striking body at the end of the forward motion of the striking body 6.

Having now fully described and ascertained my said invention and the manner in which it is to be performed, I declare that what I claim is:

1. In striking or hammering tools of the kind referred to comprising a rotary and reciprocating striking body, an anvil, cooperating faces on said striking body and the anvil whereby upon rotation of the striking body the anvil is given a blow and whereby the striking body recoils backwardly from said blow to move in an axial direction, a chamber located at the end of the striking body formed in part by said striking member in which the air pressure is varied by the axial movement of said striking body on its axial recoil, such change in pressure tending to returnthe striking body to normal striking position and means to communicate such chamber with the atmosphere when in the last named position.

2. In a striking and hammering tool as claimed in claim 1 in which the means to communicate said chamber with the atmosphere comprises means for supporting and rotating said striking body and which also forms walls of said chamber, a port leading from the supporting means to the atmosphere and means controlled by the position of said striking body to open and close communication between said chamber and the atmosphere.

3; In a striking and hammering tool, a supporting casing, an anvil reciprocating in said casing, a rotatable striking body, means within said casing to rotate said striking body, cooperating faces on the striking body and anvil whereby the anvil is given a blow by the rotation of said striking body, said supporting means being formed with an open cylindrical end within which said striking body reciprocates upon recoil from the blow delivered to the anvil, said striking body, in a portion of such recoil movement changing the air pressure in said cylinder to cause the return of said striking body to normal 

